(c) A bullet of mass 0.02 kg is fired by a gun of mass 20 kg. If the speed of the bullet is 150 ms21, calculate the recoil speed of the gun ?

24. If the mass of a body is doubled, what happens to its acceleration when acted upon by the same force ? Justify your answer.

(b) It is easier to stop a tennis ball than a cricket ball moving with the same speed. Why ?

(c) A girl of mass 40 kg jumps with a horizontal velocity of 5 ms21 on to a stationarycart with frictionless wheels. The mass of the cart is 10 kg. Find her velocity as the cart starts moving. Assume that there is no external unbalanced force working in the horizontal direction.

25. List two difference in tabular form between speed and velocity. When is a body said to have : (a) uniform velocity and (b) variable velocity. How is the average velocity of a body calculated when its velocity changes at a non uniform rate ?

26. A train starting from rest, pick up a speed of 10m/s in 100s. It continues to move at the same speed for the next 250s. It is then brought to rest in the next 50s. Plot a speed – time graph for

27. Mention the different methods of growing crops to get maximum produce. Give one example of each method. List the factors which are taken into consideration while deciding the choice of crops for each method.

28. Differentiate between capture fishing and culture fishery. Explain the advantage of composite fish culture with example. State the problems faced on adopting composite fish culture and also the solution found to solve it.

29. (a) Define the following properties of matter – (i) rigidity (ii) diffusion (iii) compressibility (b) Arrange solids, liquids and gases in the ascending order as regards the extent to which each of the above properties is exhibited them.

(c) Write any one example from your daily life experience which is based on diffusion of gases.

30. (a) When a motor car makes a sharp turn at a high speed, we tend to get thrown to one side. Why ?

(b) State Newton’s 1st and 3rd law of motion.

(c) A force of 5N gives a body of mass ‘m’ an acceleration of 10m/s2, Calculate the mass of the body in grams.